Within a couple of hours, serious internal burns can occur in the upper chest region, leading to long-term problems with breathing and swallowing – and even death.

If a child is thought to have swallowed one, they should be taken to A&E immediately.

Young children at risk

The safety body warned that small children are at higher risk due to their tendency to put things in their mouths, and people should be particularly vigilant to button batteries with a diameter of 20mm or more as they are more likely to get stuck in the throat.